Re: [PATCH 2/2] arm64: tegra: Describe Tegra234 CPU hierarchy

[Thierry Reding <thierry.reding@gmail.com>]

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On Mon, Nov 29, 2021 at 10:53:37PM +0000, Robin Murphy wrote:
> On 2021-11-29 21:06, Rob Herring wrote:
> > On Fri, Nov 12, 2021 at 02:19:04PM +0100, Thierry Reding wrote:
> > > From: Thierry Reding <treding@nvidia.com>
> > > 
> > > The NVIDIA Tegra234 SoC has 3 clusters of 4 Cortex-A78AE CPU cores each,
> > > for a total of 12 CPUs. Each CPU has 64 KiB instruction and data caches
> > > with each cluster having an additional 256 KiB unified L2 cache and a 2
> > > MiB L3 cache.
> > > 
> > > Signed-off-by: Thierry Reding <treding@nvidia.com>
> > > ---
> > >   arch/arm64/boot/dts/nvidia/tegra234.dtsi | 365 ++++++++++++++++++++++-
> > >   1 file changed, 363 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/arch/arm64/boot/dts/nvidia/tegra234.dtsi b/arch/arm64/boot/dts/nvidia/tegra234.dtsi
> > > index 104e5fdd5f8a..db24f48edc9f 100644
> > > --- a/arch/arm64/boot/dts/nvidia/tegra234.dtsi
> > > +++ b/arch/arm64/boot/dts/nvidia/tegra234.dtsi
> > > @@ -736,12 +736,373 @@ cpus {
> > >   		#address-cells = <1>;
> > >   		#size-cells = <0>;
> > > -		cpu@0 {
> > > +		cpu0_0: cpu@0 {
> > > +			compatible = "arm,cortex-a78";
> > >   			device_type = "cpu";
> > > -			reg = <0x000>;
> > > +			reg = <0x00000>;
> > >   			enable-method = "psci";
> > > +
> > 
> > > +			i-cache-size = <65536>;
> > > +			i-cache-line-size = <64>;
> > > +			i-cache-sets = <256>;
> > > +			d-cache-size = <65536>;
> > > +			d-cache-line-size = <64>;
> > > +			d-cache-sets = <256>;
> > 
> > Isn't all this discoverable?
> 
> No. The required parameters for cache maintenance by set/way are
> discoverable from the CTR, and if you're particularly lucky they might even
> happen to reflect the underlying physical cache structures, but there's
> absolutely no guarantee of that, and there definitely exist cases where they
> don't.
> 
> [...]
> > > +	pmu {
> > > +		compatible = "arm,armv8-pmuv3";
> 
> Oh, I'd missed this - per the current state of things, we should really have
> a proper compatible for the PMU as well.

Good catch! I've changed this to arm,cortex-a78-pmu since that's what
Tegra234 has.

Thanks,
Thierry

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